5 - INNATE 2 Flashcards
what is the complement system
what is the complement system made of
mostly produced in the liver
set off a chain reaction that helps to clear pathogens
what are the key mechanisms of action of the complement system
what is opsonisation
what is phagocytosis
what are the three ways in which complements are activated
classical pathway
alternative pathway
lectin pathway
how are complements activated by cleavage
initially components are inactive pro-proteases
acting as a cascade: proteolytic cleavage generates two fragments
small:
specific function
letter “a” after the name
large:
letter “b” after the name
proteolytic activity on a new substrate
what are the main outcomes of complement activation
opsonins (C3b)
anaphylatoxins (C5a)
membrane attack complex
what do the three complement activation pathways generate and what does that product do?
the three pathways generate C3 convertase
three main outcomes
cleaves C3 into C3a and C3b
what is the lectin pathway of activation
what is the classical pathway of activation
how do all pathways converge to C3 and what does C3 do after
how does the alternative pathway work
- once C3b has been produced there is an amplification loop for C3b formation (depositing more C3b on the pathogen)
this requires factor B and protease factor D
C3bBb -> C3 convetase -> C3a and C3b - when there is high C3, C3 can undergo spontaneous hydrolysis which involves factors B and D
- the alternate pathway C3 convertase (C3bBb) is very unstable
stabilized by factors called properdin (Factor P) which are secreted by neutrophils
properdin can stabilize C3 convertase since it can bind to some microbial surfaces
what are the downstream effects of C3 activation
inflammation
increase phagocytosis
pathogen lysis
how does C3 activation cause inflammation downstream effect
more signalling = cleavage of other complement molecule
C3a and C5a recruit phagocytes and promote inflammation
if present in large amounts C3a and C5a cause anaphylactic shock
how does C3 activation cause increase phagocytosis
how does C3 activation cause pathogen lysis
how does negative regulation of C activation happen
